I have thought that maturity can almost be defined as “high proficiency in a particular protocol system.” (Chiefly a large scale and nebulous protocol system that overlaps with lots of others.) if you think about it, most times when someone is called immature, the person criticizing is really accusing them of violating one or more protocols. So the accused is alleged to be violating a cardinal “ought” that they “should” know not to break, or at least a “mature” person would know.